I know now, but when I started the answer and before being interrupted six
times, there was no answer. I didn't think about going back to see if
anyone had answered before hitting the send button. Very sorry for any
aggravation caused by this oversight and I will definitely try to be more
aware in
the future.
One added thought: the band switch index on these old amplifiers get dry
and stiff. If the index is at the rear of the assembly (can't remember if the
SB220 is or not) it puts extra stress on the shaft turning torque
requirements. That can lead to a slipped shaft.
Now, the next question is: how to free up one of these indexes?
73,
Gerald K5GW
In a message dated 4/7/2010 1:14:18 P.M. Central Daylight Time,
stevek@jmr.com writes:
Already said that!
WB2WIK/6
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
On Behalf Of TexasRF@aol.com
Sent: Wednesday, April 07, 2010 11:10 AM
To: pcb4u@verizon.net; amps@contesting.com
Subject: Re: [Amps] SB220 Sick
Jay, you might want to make sure the bandswitch shaft hasn't slipped and
the input part is not on the band you think it is on.
73,
Gerald K5GW
In a message dated 4/7/2010 12:48:15 P.M. Central Daylight Time,
pcb4u@verizon.net writes:
HI all
Need some help. I have a friends SB220 that does not accept RF drive.
Following info
1) Plate voltage good at tubes
2) Looks like 30 ohm parasitic resistors/cap (aftermarket) are good,
both
tubes
3) Relay closes...TUNE position plate idles at 100ma
4) When relay closed I do have a DC path from RF input via relay to
tube
just prior to .01uf coupling capacitor.
5) In standby RF path good from INPUT to OUTPUT
6) Tubes do not glow blue
7) The tubes appear OK (physically), passed the "shame next to ear"
test
8) No grid current
9) Driving rig (TS950) shows INFINITE SWR which (to me) indicates an
open
or short (RF wise) in input.
10) 5 volt zener OK when relay energized
I am thinking it could be the .01uf coupler to the filaments
Thoughts?
Jay
W2IJ
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